Part 2 of a series by Eugene Howell
Many novice bonsai enthusiasts want to know how to care for a bonsai tree. Some have a preconceived idea that bonsai are excellent for displaying in the house on a coffee table or a shelf and want to keep them there indefinitely. Those that do so are totally ignoring the role that light plays in the health and growth of a bonsai.
Light is the second of four major environmental factors that will determine the health your bonsai tree. We discussed the first in part one of this series.
Just as particular plants species are genetically coded to grow within certain temperature ranges, the amount of light that a bonsai tree needs will be different from species to species. From a plant’s point of view there are three types of light – full sun, partial shade and full shade. You may sometimes see “partial shade” referred to as “partial sun” but the meaning is the same.
A full sun location is one that receives six or more hours of direct sunlight each day. A partial shade location receives more than three but less than six hours of direct sunlight each day. A full shade location receives less than three hours per day of direct sunlight and can include areas where there is no direct sunlight at all. It makes no difference when, during the day, the plant receives this light. It can receive it in one dose or be spread out a little at a time throughout the day. But, don’t get confused. A lack of “direct sunlight” is not the same as “no light”. You might be amazed at how many people have purchased a bonsai that preferred “no direct sunlight” and then went home and placed it on a table in a room where the curtains are closed and the lights are off every day while they’re at work.
Generally, if a bonsai tree is placed in a ‘one-step’ shadier location than it prefers e.g.., a full-sun-loving plant placed in a partial shade location, the tree will tolerate this and probably won’t die from this alone. However, it won’t grow as robustly as it would in a proper light environment. It will have longer internode distances (not good for a bonsai), fewer leaves, and will probably never develop the ramification needed to create a magnificent bonsai tree. Worse yet, if it’s placed in a ‘two-step’ shadier location e.g., in full shade, then it’s very likely it will eventually die or at least lose all its leaves. The opposite is also true. ‘One-step’ more of sunlight can usually be tolerated but the leaves will probably turn a pale green or yellowish color and many will drop off. A ‘two-step’ increase in sunlight will most likely kill a shade loving bonsai tree.
Here in central Florida there are few plants that we use for bonsai that are not full-sun-loving plants. Those that need to be placed in partial shade are generally ones from cooler hardiness zones and because our summers are so intense and hot, they need protection from the mid-day sun. Those of us who have tried to grow Acer palmatum (Japanese maple) here in Florida have long since learned that the only way to do so is to keep them in full shade.
If you have concern about whether the hot, mid-day temperatures of summer will harm a partial-shade loving bonsai tree, place it in a position where it gets full sun from sunrise until noon and then return it to a sunny location again from about 5:00pm onward. This will provide plenty of direct sun to keep it healthy, but will avoid the hottest sun in the early afternoon.
To keep your bonsai tree healthy and beautiful you must know its environmental needs. By doing so, your tree will never suffer from too much or too little sunlight.
Photo Credit: Gary Howell